The Battle Finale of Legend! (Japanese: ディアルガとパルキア！ 最後の戦い！！Dialga and Palkia! The Final Battle!) is the 152nd episode of the Diamond & Pearl series, and the 618th episode of the Pokémon anime. It aired in Japan as a one-hour special on November 12, 2009, along with The Needs of the Three! and in the United States on April 10, 2010.

Looker and Team Rocket, now disguised as Team Galactic grunts, proceed to take over the entrance to the Spear Pillar. Team Galactic leaves their headquarters via helicopter with Ash and his friends imprisoned in the same helicopter. Cynthia spots the chopper from the ground and follows in her SUV. Looker and Team Rocket, having neutralized the Galactic grunts, pretend to stand guard at the entrance with the intent of ambushing Team Galactic just as their chopper arrives and sets down. However, Cyrus and his Commanders easily see through the disguise which results in them being incapacitated by a Flamethrower attack from Jupiter's Skuntank and being put in the helicopter's cell with Ash and his friends.

Outside the gate, Saturn uses the Spear Key to unlock the gate to the Spear Pillar, the key being absorbed into the gate and changing form. Cyrus opens the gate with the Red Chain fragment in his hand, opening the pathway. The path lights up, leading down to the Spear Pillar as Cyrus and his men, except for Jupiter, head inside. Moments later, as Jupiter grows bored of having to wait, Skuntank gets hit by a Giga Impact from Cynthia's Garchomp. Cynthia confronts her as Garchomp restrains Jupiter. Cynthia frees Ash and his friends, locking down Jupiter and the Galactic grunts. Though Jupiter insists it is too late, Ash and his friends proceed into the Spear Pillar to stop Cyrus.

Inside the Spear Pillar, Cyrus and his men reach their destination, placing the Adamant and Lustrous Orbs, as well as the lake guardians, in position around the ancient ruins. Cyrus uses the power of the Red Chain to force the lake guardians to use their energies to power the orbs and begin to summon Dialga and Palkia. Charon then gives the order to fire and two bolts of Red Chain energy are shot from a cannon around the formations of two mystical energy portals. As the portals begin to take shape, their powers are quickly causing disturbances around Mt. Coronet, which Professor Rowan and Gary pick up from their lab. Dialga and Palkia start to appear at the Spear Pillar, the Red Chains quickly taking control of both. Pikachu, Piplup, and Croagunk fly in on Staraptor, Garchomp and Gliscor, destroying the cannon. Saturn sends out Toxicroak, but Croagunk jumps from Gliscor and, just as Toxicroak finishes emerging from its Poké Ball, strikes it with Brick Break to the head. Toxicroak falls to the ground knocked out to Saturn's shock, while Brock commends a happy Croagunk on a great job.

Though Cynthia is awed to meet the lake guardians, she never wanted to see them this way. Mars sends out Purugly and the Grunts send out Golbat, but Pikachu and Piplup easily put them down, allowing Ash and his friends to proceed. Pikachu, Piplup and Croagunk free the lake guardians, destroying the Red Chain fragments on their foreheads. Ash recalls Staraptor and Gliscor into their Poké Balls and he, Dawn and Brock retrieve the lake guardians. Dialga and Palkia start to disappear and it appears that Cyrus has lost; however, it emerges that he has a back-up plan—Cyrus summons more power from the Red Chain, and the formations begin to glow, causing Dialga and Palkia themselves to appear. The Pokémon strain under the power of the Red Chain as it takes control of them.

The lake guardians Pokémon draw into their powers as they telepathically ask Ash and his friends to free Dialga and Palkia. Cyrus orders the legendary Pokémon to use their powers, creating a portal into another dimension that will expand outward and consume the old world, the effects causing massive disturbances around Mt. Coronet. Ash and his friends try to attack the Red Chains holding Dialga and Palkia, but Cyrus has the legendary Pokémon use their signature moves to stop Pikachu, Piplup, Croagunk and Garchomp's attacks. Dialga's Roar of Time also proceeds to strike Ash and his friends, but the lake guardians blocks the attack.

Saturn and Mars want to go into the new world with Cyrus, but he turns on them, revealing his true intention of having the new world to himself. Ash and his friends attack again, this time destroying the Red Chains and freeing Dialga and Palkia. The portal begins to shrink, but Cyrus walks up and gets drawn into it before it fades. Mars panics and wants to go too, but Saturn holds her back as the portal disappears.

However, Dialga and Palkia continue to rampage, creating a massive black hole of negative energy that threatens to envelop and destroy the Sinnohregion. Cynthia warns them of the impending danger as the lake guardians pleads with Ash and his friends to do what they can. One by one, the lake guardians use their energies to calm Dialga and Palkia before creating a portal that sends them back to their isolated dimensions, reversing the energy levels and clearing the area around Mt. Coronet.

The lake guardians celebrates with Ash and his friends before disappearing. Back at the surface, Professor Rowan and Gary arrive. The Adamant and Lustrous Orbs are secured as Gary decides to take them back to Professor Carolina. While Team Rocket makes their getaway, the police take away Saturn, Jupiter and Mars. Cynthia thanks Ash and his friends for saving Sinnoh as they continue on their journey.